1. Field of the Invention
This invention relates to a needle used for sampling a tissue from a living body so as to diagnose or treat a disease. Specifically, the present invention relates to a needle that makes it possible to harvest a tissue sample from a living body favorably enough to reduce damage of the harvested sample to a minimum and effectively enough to obtain precise information.
2. Background Art
Needles for living bodies, such as biopsy needles and therapeutic needles, are often employed for diagnosing or treating diseases of human and animals. The needles for living bodies are pricked into skins or the like of creatures, so as to inject medicines or to pluck out tissues by use of the tips of the pricked needles. In the case where the needles are applied to human bodies and the like, they are required to damage tissues to a minimal degree. Specifically, since biopsy needles are used for sampling tissues from living bodies for the purpose of obtaining precise information of diseases, the tissue samples are harvested from organs or the like in the bodies preferably without being damaged. This is because the precise information of diseases is hard to obtain if the tissues are damaged when sampled.
Meanwhile, biopsy needles and therapeutic needles have been made of metals such as stainless steel because metals are excellent in rustproof characteristics, in elasticity and in tension resistance and also are easily formed into sharp shapes. However, since having electroconductivity and magnetism, metal needles are known to cause injury current when brought into contact with living bodies and, as a result, to damage almost all the cells in contact therewith. Accordingly, tissue samples harvested with metal needles are often so damaged that it is difficult to obtain precise information of diseases therefrom.
For coping with the above problem, it is proposed (Japanese Patent Laid-Open (KOKAI) No. 2002-85413) to adopt a metal hollow capillary needle coated with a super-hard, non-electroconductive and non-magnetic substance. This needle enables to pluck out a tissue from the aimed site without bringing the tissue into contact with the electroconductive and magnetic metal, and therefore the injury current can be avoided to keep the tissue from being damaged. Consequently, the proposed needle makes it possible to obtain precise information of diseases.
However, even if a metal needle for a living body is coated with a non-electroconductive substance like the above proposed needle, the inside wall of the penetrating hole, namely, the surface of the flow path is covered with such a thin coating film as is liable to peel off or to crack to be destroyed as time elapses. Further, when the needle is only slightly distorted, the coating film often comes off. As a result, the sampled tissue may be brought into contact with metal, and hence the effect of the coating is often insufficiently obtained. In addition, since the coated needle itself is still mainly made of metal like the conventional metal needle, it cannot solve problems of disposal after use.
In view of the above, the inventors have proposed a new needle made of only ceramics (Japanese Patent Laid-Open (KOKAI) No. 2008-307072). The proposed needle for a living body can improve the production cost as well as the damage of tissues caused by the injury current.